Method of depositing material on stepped structure

ABSTRACT

A method for depositing material is disclosed. An exemplary method includes positioning a substrate provided with a stepped structure comprising a top surface, a bottom surface, and a sidewall in a reaction chamber; controlling a pressure of the reaction chamber to a process pressure; providing a precursor; providing a reactant; and, providing a plasma with a RF plasma power, wherein by simultaneously providing the precursor, the reactant, and the plasma while controlling the process pressure to less than or equal to 200 Pa and controlling the RF plasma power to more than or equal to 0.21 W per cm2 the material is deposited on the top surface, the bottom surface, and the sidewall of the stepped structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Application No. 63/091,871, filed on Oct. 14, 2020 in the United States Patent and Trademark Office, the disclosure of which is incorporated herein in its entirety by reference.

FIELD OF INVENTION

The present disclosure relates generally to a method of depositing material and more particularly, to a method of depositing silicon nitride on a stepped structure of a substrate via plasma enhanced chemical vapor deposition (PECVD).

BACKGROUND OF THE DISCLOSURE

High density storage devices have been proposed using a 3D stacked memory structure, which includes a stepped structure. It is required to form a thin film on a selected area of the stepped structure.

Plasma Enhanced Atomic Layer Deposition (PEALD) may be applied to form the thin film on the stepped structure. However, ALD has a slow rate of film deposition.

Any discussion, including discussion of problems and solutions, set forth in this section, has been included in this disclosure solely for the purpose of providing a context for the present disclosure, and should not be taken as an admission that any or all of the discussion was known at the time the invention was made or otherwise constitutes prior art.

SUMMARY OF THE DISCLOSURE

This summary is provided to introduce a selection of concepts in a simplified form. These concepts are described in further detail in the detailed description of example embodiments of the disclosure below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

In various embodiments, a method of depositing material on a stepped structure is provided. The method may comprise positioning a substrate provided with a stepped structure comprising a top surface, a bottom surface, and a sidewall in a reaction chamber; controlling a pressure of the reaction chamber to a process pressure; providing a precursor; providing a reactant; and, providing a plasma with a RF plasma power wherein by simultaneously providing the precursor, the reactant, and the plasma while controlling the process pressure to less than or equal to 200 Pa and controlling the RF plasma power to more than or equal to 0.21 W per cm² the material is deposited on the top surface, the bottom surface, and the sidewall of the stepped structure.

In various embodiments, the RF frequency may be in the range of 13.55 to 27.13 Hz.

In various embodiments, the method may comprise depositing silicon nitride (SiN) on the top surface, the bottom surface, and the sidewall of the stepped structure.

In various embodiments, the method may comprise providing a precursor comprising a halogenated silane. In various embodiments, the halogenated silane may be dichlorosilane, trichlorosilane, or hexachlorodisilane.

In various embodiments, the reactant may comprise a nitrogen reactant. In various embodiments, the nitrogen reactant may be NH₃.

In various embodiments, positioning the substrate in the reaction chamber may comprise positioning the substrate in between, and parallel to two electrodes and the plasma may be provided by applying RF plasma power to at least one of two electrodes.

In various embodiments, the wet etch rate of the material deposited on the sidewall divided by the wet etch rate of the material deposited on the top may be larger than 2.5.

In various embodiments, the method may further comprise providing an etchant to etch a sidewall portion of the deposited material to remove the side wall portion.

In various embodiments, providing an etchant may comprise providing a solution of hydrogen fluoride (HF). In various embodiments, providing an etchant may comprise providing a solution of phosphoric acid.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

A more complete understanding of exemplary embodiments of the present disclosure can be derived by referring to the detailed description and claims when considered in connection with the following illustrative figures.

FIG. 1 is a schematic representation of a PECVD (plasma-enhanced chemical vapor deposition) apparatus for depositing a dielectric film usable in an embodiment of the present invention;

FIG. 2 is a timing chart of a PECVD process;

FIG. 3 is a schematic diagram of showing a model of ion bombardment and impurities concentration in a film on a top surface and a bottom surface and a sidewall of a stepped structure;

FIG. 4A is a schematic diagram of showing a film on a top surface and a bottom surface and a sidewall of a trench structure; and

FIG. 4B is a schematic diagram of showing a film on a top surface and a bottom surface and a sidewall of the trench structure after wet etching.

It will be appreciated that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help understanding of illustrated embodiments of the present disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Although certain embodiments and examples are disclosed below, it will be understood by those in the art that the disclosure extends beyond the specifically disclosed embodiments and/or uses of the disclosure and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the disclosure should not be limited by the particular embodiments described herein.

The illustrations presented herein are not meant to be actual views of any particular material, apparatus, structure, or device, but are merely representations that are used to describe embodiments of the disclosure.

As used herein, the term “substrate” may refer to any underlying material or materials that may be used, or upon which, a device, a circuit, or a film may be formed.

As used herein, the term “film” and “thin film” may refer to any continuous or non-continuous structures and material deposited by the methods disclosed herein. For example, “film” and “thin film” could include 2D materials, nanorods, nanotubes, or nanoparticles or even partial or full molecular layers or partial or full atomic layers or clusters of atoms and/or molecules. “Film” and “thin film” may comprise material or a layer with pinholes, but still be at least partially continuous.

The process cycle may be performed using any suitable apparatus including an apparatus illustrated in FIG. 1, for example. FIG. 1 is a schematic view of a PECVD apparatus, desirably in conjunction with controls programmed to conduct the sequences described below, usable in some embodiments of the present invention. In this figure, by providing a pair of electrically conductive flat-plate electrodes 4, 2 in parallel and facing each other in the interior 11 (reaction zone) of a reaction chamber 3, applying HRF power (13.56 MHz or 27 MHz) 20 to one side, and electrically grounding the other side 12, a plasma may be excited between the electrodes. A temperature regulator may be provided in a lower stage 2 (the lower electrode), and a temperature of a substrate 1 placed thereon may be kept constant at a given temperature. The upper electrode 4 may serve as a shower plate as well, and precursor and reactant gas may be introduced into the reaction chamber 3 through a gas line 21 and a gas line 22, respectively, and through the shower plate 4. Additionally, in the reaction chamber 3, a circular duct 13 with an exhaust line 7 may be provided, through which gas in the interior 11 of the reaction chamber 3 may be exhausted.

Further, a transfer chamber 5 disposed below the reaction chamber 3 may be provided with a seal gas line 24 to introduce seal gas into the interior 11 of the reaction chamber 3 via the interior 16 (transfer zone) of the transfer chamber 5 wherein a separation plate 14 for separating the reaction zone and the transfer zone may be provided (a gate valve through which a wafer is transferred into or from the transfer chamber 5 is omitted from this figure). The transfer chamber may be also provided with an exhaust line 6. In some embodiments, the deposition of multi-element film and surface treatment may be performed in the same reaction space, so that all the steps may continuously be conducted without exposing the substrate to air or other oxygen-containing atmosphere. In some embodiments, a remote plasma unit may be used for exciting a gas.

In some embodiments, a multiple chamber module (two or four chambers or compartments for processing wafers disposed close to each other) may be used, wherein a reactant gas and a noble gas may be supplied through a shared line whereas a precursor gas may be supplied through unshared lines.

A skilled artisan will appreciate that the apparatus includes one or more controller(s) (not shown) programmed or otherwise configured to cause the deposition and reactor cleaning processes described elsewhere herein to be conducted. The controller(s) may be communicated with the various power sources, heating systems, pumps, robotics, and gas flow controllers or valves of the reactor, as will be appreciated by the skilled artisan.

With additional reference to FIG. 2 and FIG. 3, a method for deposition material is illustrated. The method includes positioning a substrate provided with a stepped structure comprising a top surface, a bottom surface, and a sidewall in the reaction chamber 3; controlling a pressure of the reaction chamber 3 to a process pressure; providing a precursor; providing a reactant; and providing a plasma with a RF plasma power. The material may be deposited on the top surface, the bottom surface, and the sidewall of the stepped structure by simultaneously providing the precursor, the reactant, and the plasma, which is Plasma Enhanced Chemical Vapor Deposition (PECVD) process. PECVD is a chemical vapor deposition process used to deposit thin films from a gas state (vapor) to a solid state on the substrate. Chemical reactions are involved in the process, which occur after creation of a plasma of the reacting gases. The precursor gas and reactant gas continue to flow to the reaction chamber 3 while RF plasma power is continuously applied to the electrode 4.

By adjusting bombardment of a plasma excited by applying voltage between two electrodes 2, 4 between which the substrate is placed in parallel to the two electrodes 2, 4, a top/bottom portion of the dielectric film formed on the top surface and the bottom surface and a sidewall portion of the dielectric film formed on the sidewalls can be given different chemical resistance properties. A plasma is a partially ionized gas with high free electron content (about 50%), and when a plasma is excited by applying AC voltage between parallel electrodes 2,4, ions are accelerated by a self dc bias (VDC) developed between plasma sheath and the lower electrode 2 and bombard a film on a substrate placed on the lower electrode 2 in a direction perpendicular to the film (the ion incident direction). The ion bombardment may be modulated by tuning the pressure and RF power. The lower the pressure and the higher the power, the higher the ion bombardment becomes, resulting in low impurities in top/bottom portions of film. A pressure of the reaction chamber 3 may be controlled less than or 200 Pa or less or equal to 150 Pa. RF plasma power may be controlled more than or equal to 0.21 watt per cm² (150 W for 300 mm wafer), preferably 0.28 watt per cm² and more preferably 0.35 watt per cm².

In some embodiments, the film may be a SiN film. The SiN film may comprise providing a precursor comprising halogenated silane and a reactant comprising nitrogen-containing reactant. The halogenated silane may be dichlorosilane (DCS), trichlorosilane, or hexachlorodisilane. The nitrogen-containing reactant may be NH₃.

In some embodiments, according to the difference in the film properties between the top/bottom portion of the film and the sidewall portion of the film, the sidewall portion of the film is more predominantly etched than the other by wet etching. The wet etch rate of the material deposited on the sidewall divided by the wet etch rate of the material deposited on the top may be larger than 2.5, preferably larger than 3 and most preferably larger than 3.5. The wet etching may be conducted using a solution of hydrogen fluoride (HF), for example.

The present invention is further explained with reference to working examples below. However, the examples are not intended to limit the present invention. In the examples where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation. Also, the numbers applied in the specific examples can be modified by a range of at least ±50% in some embodiments, and the numbers are approximate.

EXAMPLES Example 1

SiN films were formed on Si substrates (ϕ300 mm) having a stepped structure by PEALD and PECVD, which were conducted under the conditions shown in Table 1.

TABLE 1 (numbers are approximate) PEALD PECVD Process 1^(st) 2^(nd) 1^(st) 2^(nd) Gas Ar [slm] 1.5 3 0.75 1.5 Flow N2 [slm] 0.5 1 1.5 0.75 Rate DCS [slm] 1 1 0.1 0.1 NH3 [slm] 3 0.5 0.5 0.5 BTL1 Ar [slm] 1 2 0.75 0.75 BTL2 Ar [slm] 1 2 0.75 0.75 Seal N2 [slm] 2 2 0.5 0.5 Pressure [Pa] 533 400 200 150 RF power [W] 100 150 150 250

After taking out the substrate from the reaction chamber, the substrate was subjected to wet etching under the conditions shown in Table 2 below.

TABLE 2 (numbers are approximate) Conditions for Wet etching Etching solution HF 0.05-5% Etching solution 10 to 50° C. (preferably 15 to 30° C.) temperature Duration of etching 1 sec to 5 min (preferably 1 to 3 min) Etching rate 0.1 to 5 nm/min (preferably 0.5 to 2 nm/min)

For wet etching, any suitable single-wafer type or batch type apparatus including any conventional apparatuses can be used. Also, any suitable solution for wet etching including any conventional solutions can be used.

The results are shown in Table 3 and FIG. 4. WER selectivity is defined by the ratio of WER on the sidewall portion and the WER on the top portion.

TABLE 3 (numbers are approximate) PEALD PECVD Process 1^(st) 2^(nd) 1^(st) 2^(nd) Pressure [Pa] 533 400 200 150 RF power [W] 100 150 150 250 WER selectivity (Side/Top) 1.9 2.2 1.9 3.8 Depo rate [nm/sec.] 0.03 0.02 0.63 0.57

As shown in Table 3, the wet etch rate of the sidewall portion increased as RF power increased and pressure decreased, whereas the wet etch rate of the top portion decreased as the RF power increased and pressure decreased. The threshold RF power of PECVD process was approximately 150 W and the threshold Pressure is 200 Pa. It can be understood that when RF power applied between the electrodes is higher than approximately 150 W and pressure is lower than approximately 200 Pa, the sidewall portion of the film can be removed selectively relative to the top/bottom portions of the film. Further, the deposition rate of PECVD is much higher than that of PEALD.

The example embodiments of the disclosure described above do not limit the scope of the invention, since these embodiments are merely examples of the embodiments of the invention. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the disclosure, in addition to those shown and described herein, such as alternative useful combinations of the elements described, may become apparent to those skilled in the art from the description. Such modifications and embodiments are also intended to fall within the scope of the appended claims. 

What is claimed is:
 1. A method for depositing material, comprising: positioning a substrate provided with a stepped structure comprising a top surface, a bottom surface, and a sidewall in a reaction chamber; controlling a pressure of the reaction chamber to a process pressure; providing a precursor; providing a reactant; and, providing a plasma with a RF plasma power, wherein by simultaneously providing the precursor, the reactant, and the plasma while controlling the process pressure to less than or equal to 200 Pa and controlling the RF plasma power to more than or equal to 0.21 W per cm² the material is deposited on the top surface, the bottom surface, and the sidewall of the stepped structure.
 2. The method according to claim 1, wherein the RF frequency is in the range of 13.55 to 27.13 MHz.
 3. The method according to claim 1, wherein the method comprises depositing silicon nitride (SiN) on the top surface, the bottom surface, and the sidewall of the stepped structure.
 4. The method according to claim 1, wherein the method comprises providing a precursor comprising a halogenated silane.
 5. The method according to claim 4, wherein the halogenated silane is dichlorosilane, trichlorosilane, or hexachlorodisilane.
 6. The method according to claim 1, wherein the reactant comprises a nitrogen reactant.
 7. The method according to claim 6, wherein the nitrogen reactant is NH₃.
 8. The method according to claim 1, wherein positioning the substrate in the reaction chamber comprises positioning the substrate in between, and parallel to two electrodes and the plasma is provided by applying RF plasma power to at least one of two electrodes.
 9. The method according to claim 1, wherein the wet etch rate of the material deposited on the sidewall divided by the wet etch rat of the material deposited on the top is larger than 2.5.
 10. The method according to claim 1, further comprising providing an etchant to etch a sidewall portion of the deposited material to remove the side wall portion.
 11. The method according to claim 10, wherein providing the etchant comprises providing a solution of hydrogen fluoride (HF).
 12. The method according to claim 10, wherein providing the etchant comprises providing a solution of phosphoric acid. 